Keeping your bento lunch safe (Reviewing bento basics)

11 Jan 2010 by maki

Note: This bento safety article is one of the first ones I posted here on Just Bento, back in November 2007. I’ve edited it and added some more information, especially since more and more new people are coming to the site. Even if you’re a veteran bento maker, it’s good to go over the basics occasionally!

A traditional portable bento box meal is meant to be eaten eaten at room temperature. It’s typically made in the morning, then held for a few hours until lunchtime, also at room temperature. Millions and millions of Japanese people eat bentos like this (as well as an increasing number of people all around the world). There are some basic, time-tested precautions to take to ensure that your bento box meals will be tasty and safe when you tuck into them.

Thoroughly re-heat then cool any cooked food before packing

Using leftover and pre-cooked food reduces the time needed to assemble your bento in the morning. But the longer food has been lying around, even in the refrigerator, it gets less fresh and edible. Re-heating cooked food helps to kill off any micro-organisms that may have started to grow.

The best way to re-heat things in my opinion is in a pan, rather than the microwave, because the surface is where the microorganisms are likely to have formed, and the high heat of a pan will kill those off immediately. This is particularly important with meat, fish and even vegetable proteins. Japanese bento books usually recommend this.

In some cases it can be okay to pack food direct from the refrigerator, such as pre-made salads, instant pickles, and so on. Do use common sense though; packing leftovers from the night before is usually okay, but leftovers from 3 days ago get iffy. When in the slightest doubt, heat it through and cool it down.

Don’t use raw or undercooked fish or meat

You’re probably not going to be carrying a steak tartare to work for lunch. But you might think about sushi. Don’t. Raw fish is not safe unless it’s eaten immediately. (I’ve seen a couple of French bento cookbooks that use raw-fish sushi. They made me shudder, thinking of the people who might get sick eating hours-old raw fish.) If you have leftover sushi from the night before, throw it out or cook the fish if you must. (Yes you might have been ok eating leftover sushi, but you were lucky.)

Sushi that uses cooked or preserved foods (egg, boiled shrimp, broiled eel (unagi), vegetables like kanpyou (dried gourd strips), pickles) is ok, though always use caution. Futomaki, the colorful big pinwheel sushi, usually only uses cooked items so is usually ok. There are also special sushi varieties that are meant to be long-keeping, such as saba zushi (marinated horse mackerel that is pressed onto a log of rice), but you rarely see these outside of Japan. Sushi rice itself keeps fairly well, due to the vinegar and salt that flavors it.

Meat that has been cooked on the surface (e.g. roast beef that’s pink on the inside) is usually ok, but when in doubt pack such foods with an ice pack to keep them cool. Certain meats such as pork and chicken always need to be cooked through when used for bentos (and for other purposes too mostly.)

Avoid very moist or undercooked proteins in hot weather

Undercooked meat is not safe, and neither is undercooked or raw fish. But undercooked or moist protein of any kind should be avoided when the weather is hot. Plain tofu, for example, that hasn’t been cooked through thoroughly, can be unsafe, and should be reserved for the cooler months. Or, use an icepack or other cooling device for safety. (Most tofu recipes on Just Bento will be totally cooked through, so are safe. For simple stir-fries and so on, I prefer using fried tofu over plain tofu because of the lower initial moisture content.)

Conversely, - and this may seem like common sense, but needs to be said - don’t use tofu that is bad in the first place. I have tasted so much bad tofu at various restaurants, and even in people’s homes. If the tofu smells or tastes sour or rotten or ‘off’ in any way, it should be tossed. To keep tofu that’s been opened fresh, totally immerse in fresh water and seal completely. Change the water at least once a day.

Tamagoyaki, the slightly sweet Japanese omelette, is a bento staple. But to be really good it has to be slightly moist in the middle. So, be sure to use fresh eggs, and to cool it down completely before packing into the bento box. (I’ve been expermenting a bit with freezing sliced tamagoyaki recently; I’ll report back soon with the results.)

Home made mayonnaise is delicious, but should be used with caution, in foods like tuna salad. Commercial mayo has all kinds of preservatives in it that we’d rather not think about, but do keep our tummies happy. (See freezing tuna salad.)

Keep cool foods separate from hot

Remember the McDLT? The gimmick with that burger was the two-part styrofoam container, with one side for the lettuce and tomato, and the other for the burger and bun. (Here’s an old commercial for the McDLT featuring Jason Alexander, who played George Costanza on Seinfeld.) There was logic behind this rather environmentally unfriendly packaging. Any foods that should be kept cool, such as raw fruits and vegetables, should be kept in a separate container from the cooked foods, even if the cooked foods have had a chance to cool down. This will keep veggies fresh and crisp.

Do you need an ice pack?

Unless an ice pack is specifically called for, all the complete bento lunch ideas as well as the individual component recipes are meant to be safe to eat without refrigeration, if the safety precautions on this page are followed.

In hot weather, it’s safer to pack an ice pack with the cool food. One trick is to freeze a juice carton or a small plastic bottle filled with the beverage of your choice, and to freeze it. Pack that with your lunch box, and it acts as an ice pack and will have defrosted enough to drink by lunch time.

If you’re carrying a bento meal that’s meant to be consumed more than a few hours later — e.g., a bento packed in the morning meant to be eaten in the evening for a night class — use an ice pack to be on the safe side, or use the foods that keep food fresher longer listed below. (An umeboshi onigiri (rice ball) will even keep for a couple of days.)

Thermal lunch containers don’t guarantee safety!

Some people assume that using a thermal lunch container such as Zojirushi’s Mr. Bento will guarantee food safety. Don’t fall into that trap! Do remember that a thermal lunch container maintains heat at a certain level for longer than a regular lunch or bento box. So, if you pack a lukewarm, moist lunch, your food will become a great cosy breeding ground for the nasties. Be sure to follow the manufacturer’s instructions for these thermal containers, and pack either piping hot or thoroughly cooled food in them.

Try to only use freshly cooked or frozen rice

Plain rice can actually go bad pretty fast, since it’s so moist. It can also become inedible quite fast if it goes a bit dry and hard, especially in the desert-like atmosphere of a typical refrigerator. This is why a rice cooker with a timer function is a very useful thing to have.

If you do cook rice the day before, make sure it’s wrapped up completely before storing in the refrigerator. If you want to keep rice longer, it’s best to freeze it. You can carry the frozen rice as-is in a block (especially in hot weather), or heat it through completely in the microwave or by steaming, and cool down completely.

If you live in a very warm and humid climate, you may want to consider carrying rice in the form of sushi rice or as well-salted onigiri only in the summer - or with umeboshi (see below).

Certain foods that help keep things fresher

Traditionally, umeboshi (pickled plum) has been used in bentos and as onigiri filling. The traditional hinomaru bento, a bento box filled with white rice sporting one, lone umeboshi in the middle, is a very good keeper. (Incidentally, the logo for Just Bento is inspired by the hinomaru bento.) Umeboshi may have antimicrobial qualities, as do (supposedly) shiso leaves.

Fresh, nontoxic green leaves used as dividers and wrappers are also supposed to have antibacterial qualities. These are not edible. The most popular one is fresh bamboo leaves. (Dried bamboo leaves are also used as as wrappers, but don’t have the same antimicrobial qualties as fresh.) Banana leaves, used in South-East Asian cuisine, may have similar properties.

Wasabi and ginger may also help to keep things fresher. Try using wasabi to flavor vegetables (example: broccoli with wasabi sauce), or tucking some pickled ginger in the corner of your bento.

Salt is a time tested preserver, so the salt you put on the surface of onigiri is not just for flavor - it’s to keep the rice fresher longer.

Sugar can also act as a preservative (think of jams and preserves), though you need to use it in some quantity.

Vinegar is also a preserver. Salty or vinegary foods keep longer than foods with little seasoning. Sushi rice keeps better than plain rice because of the vinegar, salt and sugar.

Anti-bacterial bento boxes and sheets

Some bento boxes, such as this one on the J-List/JBox site, have an anti-bacterial silver ion coating, which is supposed to keep your food safer for longer. You can also find antibacterial bento sheets designed to be placed on top of the food. However, using these products doesn’t mean that you shouldn’t follow the safety precautions listed on this page! Personally, I don’t use these products (though I do have the bento box linked to, just because it’s a big black one that’s perfect for The Guy’s bentos) because I have a feeling they just give a false sense of security.

Wash your used bento containers and implements completely

A no brainer perhaps. But don’t try to re-use an unwashed bento box or Mr. Bento dish! Wash and dry everything thoroughly before you use them again. The same goes for any eating utensils, such as chopsticks, forks and spoons, and picks, and all the cooking implements you use to prepare your bento. As pointed out in the comments, don’t forget to wash the gaskets and edges of the lids and so forth too.

Be careful of tasting while cooking

Did you know that you can contaminate food by tasting it? Example: if you dip a spoon into a pot of soup, taste from that spoon, then put the spoon back in to the pot, you’ve added whatever germs are in your mouth to the soup. This may not be a big deal if you’re eating the food right away, but if you’re going to be carrying it around for a few hours you want to be extra cautious. If you do need to taste while cooking, don’t use the utensil you put into your mouth back into the food.

Don’t forget about your hands either! Don’t use your fingers to pick up food and put it in your mouth while you’re making onigiri for example. And of course, you should wash your hands thoroughly before handling any food.

Try not to over-handle the food

If you are a budding cute bento or charaben artist, be careful of over-handling food that you are bringing for bento, especially in hot weather. Try to avoid using your hands as much as possible. If you need to practice your decorative bento skills, you may want to consider eating the results immediately. There’s no rule that says rice shaped like Totoro has to be only be eaten for bento! Skilled charaben artists use chopsticks, toothpicks and tweezers to avoid over-handling the food.

Conclusion: Be safe, not sorry!

My aim is not to scare you off of making bento lunches by any means. But it’s better to take just a few commonsense precautions. Bentos should make you healthier, not sick!

45 comments

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If you are using a bento box, don’t forget that part of the cleaning process includes removing any seals in the rim of the lid-many people overlook these and they are a breeding ground for yuckiness. :)

Bento lunches are usually eaten at room temperature, including the rice - since it’s assumed that a way of heating it up at eating time is not available. (Though of course you can make bento lunches to heat up, if you have the facilities to do so). The standard safety procedure for rice used for bento is to heat it through in the morning (= a few hours before eating), if you’re using leftover rice. Hope that answers your question!

I was wandering, when I cook the foods I want to use in my bento, could I place it in the fridge overnight? And then take it with me the next morning?

Also, you said that freezing the foods helps preserve them, so if I let them cool after cooking them and then freezing them and then take it with me in the morning, would it be ok?
But then I got thinking, would it be safe to freeze it all packed in my Bento?

I'm not sure if that would cause any moistness in it or not, because then it would thaw out.
What do you think?

I have a question about cooling down the food all the way before closing the bento box, since i'm extremely new to making bento lunches.
It's specifically about rice. How do you cool the rice down without it getting hard? letting it sit out made mine hard, i also tried putting it in the fridge and it got hard also so i'm not sure what to do :/

i am starting to pack bento lunch for my 5year old's school lunch what do you think i should do to keep his lunch safe if he has no mircowave? make his food the night before and mircowave it in the morning?? or just make stuff meant to be eaten cold??

milk, if you make things the night before, you will either want to heat it through thoroughly then cool it down again in the morning to room temperature (the heating it through kills off most harmful microbes) and/or packing it with an ice pack, especially if the weather is very hot. Remember also that things 'meant to be eaten cold' (e.g. raw vegetables) can also harbor and grow harmful microbes so follow the safety tips above for packing any lunch.

Boilded eggs--I live in the Southeast US, where it is still quite hot and humid right now. Should I pack boiled eggs in my family's bento boxes, and if so, should I reheat them before I pack them, or send them cold with an ice pack?

Also, regarding eggs and food safety, would there be any difference between using pasteurized eggs for mayonnaise, etc. vs. regular eggs?

If the weather is very humid and hot, I would recommend taking every safety precaution. See the Summer Bento Safety post linked to from this page. Basically you should try to keep your bentos cool and insulated, with an ice pack. As for mayonnaise, for bentos I don't rick using homemade even though it tasted better; i stick to commercial mayonnaise. If you do make your own though, pasteurized eggs are a good idea - and keep whatever you use the mayo for cool (unless the mayo itself is cooked.)

This is an excellent article that every bento packer should review periodically. I gave my two nieces and their husbands bento boxes and accessories for Christmas. In order that they start off the safe way, I printed out these guidelines and put them in a folder along with the rest of the gifts. I'm delighted to say that they have begun using their bento gear and reading Justbento!

I'm living with a woman (my future-MIL) who thinks it's acceptable to eat unfrozen leftovers from over three weeks ago, so I'm REALLY not getting a kick out of this. (Well, she doesn't eat them, but tries to force us to.)

This woman has no idea how to scale her cooking, and no concept of food storing practice. My boyfriend and I spent Christmas eve out with my family, so she cooked an entire ham for her and her 13 year old daughter who probably had two bites and was done.

Then - THE NEXT DAY, when there was still probably 3 lbs of ham left, on Christmas, she cooked an ENTIRE turkey - which, by the way, she didn't start cooking until 1 PM to eat dinner at 6 (resulting in a pink turkey), because she didn't want to get out of bed despite the fact that her kids were waiting for her to open their presents. (She ended up taking all the presents back to the store the next day too.)

Oh, did I mention that she knew the two of us weren't going to be there for dinner, and cooked the WHOLE turkey anyways? My boyfriend and I were at her mother's house for dinner, and we took the 13 yo with us - oh, and since my MIL is fighting with her mother, she, as I mentioned, took all of the 13yo's presents back to the store the next day all because the kid wanted to see her grandmother on Christmas.

Now, three weeks later, she keeps trying to get us to eat the ham. I managed to use up the turkey, but since I don't eat red meat I didn't touch the ham. She keeps threatening to make us eat Rice-A-Roni with the mouldy ham in it, but I side step her with "Oh, I already took something out to cook later. Maybe another night..."

Sorry to rant... I cook delicious food for them, and all I get in return is a sink full of dirty dishes, and a disgusting kitchen to work in. (MIL is trying to "breed" her purebred shedding-yappers who are confined to, of all places, the kitchen. For two years, these two dogs have not sucessfully copulated ONCE. I think the girl dog is a lesbian...) If you laughed at this story please let me know, because that will at least make me feel better. I appreciate MIL letting me stay with them for my Winter Break from school, but...seriously... the woman doesn't just have issues, she has a subscription.

This was hilarious! I enjoyed it immensely and thank you for writing it. I was enjoying the Bento safety reminders, making mental notes and, as usual, went through the comments and Q&A for further information. This was a lovely piece (though it caused some cringing) to end with.
Thanks for all of it!

Terrifying Update!: She made soup with the ham yesterday. Luckily for us, once she gets around to making soup she usually doesn't expect us to eat any of it. She makes a huge kettle of soup about twice a week. I don't know why she does this. She usually ends up throwing it away. The worst part is that she hasn't cleaned either of the huge kettles she used last week to make soup in, nor any of the utensils. She has today off work (my company doesn't care about black people I guess) so I'm hoping she washes her dishes so I can cook later :(

Also, her dogs woke me up at 4:30 this morning to pee. She sleeps through their barking. So either I have to get up and let them out, or they will pee on the kitchen floor.

Of course, no one said I had to let them back in... (I'm... not a dog person.)

Your story (and it's terrifying update) made me a laugh a bit, and cringe a bit more. I totally sympathize! My guy and I escaped living with my future father in law four months ago. The situation there was similar, minus the pets and any semblance of cooking on ffil's part. I got in trouble for throwing out food that had been expired for *months*. He had a lecture about how his parent's didn't need expiration dates, they just determined if food was good or not be smelling it and eating a small portion. 'Cause you know, botulism wasn't a problem back in the forties or anything. Expiration dates are apparently some sort of government plot to make us buy food more often.

I'm hoping this doesn't come across as stupid but I wanted to be sure. Basically I have a question. I'm a student and work part-time so don't have time to make food in the morning so tend to make/pack my bentos the evening before (mostly always cooked from scratch). I pack my meal into my bento box (after it's cooled), seal it and then put it in the fridge, take it out in the morning and then put it in the fridge when I get into uni (no more than a 30min interval from one fridge to another). I live in the UK so the temperature is moderate. When I'm ready to eat, around 1/2pm, I either reheat it in the microwave for a bit or wait for it to get to room temperature and then eat it. Would you say this is a safe practice or am I better off heating it first thing in the morning or what should I be doing? I haven't been ill from it so far but obviously I don't want to tempt faith.

I've just cooked some tonkatsu for a bento and I've put it in the fridge. If I reheat it in a microwave the next morning and leave it from 8:00am to 1:15pm, will it still be safe to eat? If not, any ideas on how to store it for five hours so it stays edible? Thanks :D

So, if you have a fridge at work, and will be putting your bento lunch in there as soon as you get to the office and leaving it there til it's time to eat, is reheating leftovers before packing them still a necessity? Would there be any different guidelines for refrigerating your bento, since it's sort of a nonstandard practice?

I've been making bento for my husbands lunch for about 9 months now. I live in North Carolina, USA. I DO NOT make charaben lunches, although I admire them and love the thought of being able to one day make them for my 3 yr old daughter. I can't imagine what it would be like to have my child picked on or ridiculed because her lunch wasn't up to some people's standards. I'm just grateful that I do have the time and energy to make the ones I do make. They are not flashy; they are practical, accessible and edible and the only person that should matter is the person that is eating them. kasyno online

hi, three questions. I'm sorry I didn't intend it to be 3 in the beginning...

First, probably a dumb question since you've mentioned it a couple times but mayo-based dishes are okay in bento that won't be refrigerated, assuming the mayo is store-bought of course? My family has always been a stickler about leaving mayo out, but I really want to use it in bento. Is an ice pack necessary? I like, for instance, to stuff onigiri with tuna salad, so I'd like to leave it at room temperature to eat and not refrigerate.

2. Also, undercooked eggs. I love them. I see lots of Japanese bentos have them, but I think eggs in Japan are fresher than in the U.S.? If I can find pasteurized eggs, though, is it possible to use them in my bento without being fully cooked?

3. Quail eggs. I can't find fresh here. I can only find huge cans at the Asian market. Can you freeze or otherwise store them somehow? It's such a waste opening a huge can only to use a couple.

And thank you for all of the helpful information you've provided with this website!

Store bought mayo should be okay as long as you don't leave your food out for too long, or in too warm/moist conditions. In the summer you may want to use an ice pack if you live in a hot, humid area.

I personally stay away from using undercooked eggs in the U.S. or anywhere where the eggs are not date-stamped or otherwise guaranteed to be fresh. In Japan, since so many people eat eggs raw (for breakfast and other uses, e.g. even on curry rice) there's a lot more attention paid to ensuring that eggs are safe to eat raw. In Europe in general too, people eat undercooked eggs (e.g. in omelettes, the way they should be) so there's more attention paid to egg safety. Vs. the Egg Council or whatever it is in the U.S. which shirks its responsibility by saying 'eggs are safe if cooked thoroughly' (thus ruining the texture) blahblah. But anyway....so yes I do stay away from posting undercooked-egg recipes here on JustBento. If you have access to fresh, safe eggs by all means go for it.

Quail eggs...frozen boiled eggs turn a horrible texture I'm afraid. (I don't use quail eggs much either, though I can get a hold of them, because they are expensive!)

It pains me that us Americans can't eat eggs properly like the rest of the developed world...>_< And a shame that I won't be able to use the quail eggs either, but thank you very much for answering all my questions!

Sushi is fine in bentos, as long as you're not using raw fish. Take a look at my Sushi Roll Bento article. I would suggest an icepack, rather an refrigeration, for optimal taste and food safety, especially since you're using tuna mayo. Refrigerated rice tends to get rather hard and inedible, but an ice pack should keep the sushi cold enough without making it go ice cold (keep an insulated layer between your box and the ice pack).

Cooking the items thoroughly is very important. I didn't cook a chicken breast all the way through, and gave myself a nasty case of food poisoning. Now I cook my chicken until the juices run clear, even if it means my chicken is a little dry so be it.

Great post. This covers just about everything I could think of. Recently, I've noticed more and more students using ice packs here in Japan. It also seems like they tend to bring more sandwiches to school in the summer time.

nice article, just received my bento box, watcheda lot of videos about it, and am eager to make my first bento lunch.
Just one thing in your text shocks me : you write that raw fish should not be used in bentos.

Mmm... so that means that, to the contrary of what I planned, I can't put some sashimis in.
BUT you write that some french books say it's allowed!

Raw fish, kept at room temperature, may turn unhealthy within hours. That's the reason why it is not recommended to include it in bentos. If you make a suitable bento, and assure that you can keep it cooled at the appropriate temperature all the time, it will be your decision…

hum...
I remember when we were travelling by train in Japan..sometimes when we picked up the bentos from the station they would give it to us from the fridge and not heat it.
I was hoping that some bentos are ok if I pack it at night and eat it out of the fridge the next day.
If i don't have access to microwave should I let it sit outside the fridge until it's room temperature?

Are all your recipes microwavable if I pack my food at night?
I love the bento boxes in japan but I hate how it's plastic or stainless steel.
I avoid microwaving anything that's in plastic...and stainless steel is self explanatory :)
Do you know if there are glass bento boxes available?
If I really don't have to reheat my food, then the stainless steel will work too.

This article is awesome. But would it be possible to be able to reheat pasta as a side dish, since I have the mrs. Bento box, with those hand warmers? I know it sounds ridiculous, but I'm going out to a far place where there's no accessible microwave. Pasta just feels and taste weird if it's cold. Thanks!

I am also new to Bentos and would love to start using them for lunch. However, I would be packing my lunch at around 7:30 am but wouldn't be able to eat it until around 1pm or so. Is it still okay to eat room temp food after sitting for this long? Thank you and I apologize for this silly question. :)

Thanks for all this information. I just bought your book on Amazon.com and it is very well written. A great job. Me and my 17 year old daughter are going to give the Bento box a serious try. Such a great way to portion out food and it really can be more exciting than just a boring sandwich and chips. I am a professional cook with a culinary degree (the chef word is over used) and I plan to explore all of these wondeful Japanese foods that I know so little about. I am also wanting to make a special Bento for my wife who has stage 4 breast cancer and cannot really cook right now. If she has a healthy packed Bento while I am at work I will feel much better about not being home for 8 hours. She is picky. She thinks the book is wonderful and I got her excited about the idea. Thank you again for the informative and friendly website. I also have a blog but rarely have time to post. Its only for fun. It is www.wrestlingwithfood.com and maybe as I learn more about this I will talk about the Bento box and refer people to this and your other blog. Keep it up.